Rotary electrical connectors are used in a variety of applications where one part must mechanically rotate with respect to another part while retaining an electrical connection between the two. Where the required extent of rotation is small, typically less than one complete revolution, hardwired electrical connections can be used. However, hardwired connections can be difficult and expensive to make, especially where such connections must be made at remote locations or in confined spaces.
For larger required rotations, on the order of several revolutions, wraparound wire arrangements are available. In other instances, the connector must permit an arbitrarily large extent of rotation. In such a connector, electrical connection must be maintained, and the mode of connection cannot hinder the rotational movement. For these applications, the most common type of connector is a slip ring system. A plurality of slip rings in side-by-side arrangement extends along the length of a rotating shaft. Stationary brushes make contact to the individual slip rings. Unfortunately, such systems are typically expensive, due to the number of parts, and can be too bulky for some applications.
Mohi Sobhani addresses some of the foregoing problems in his patent entitled xe2x80x9cRotary Electrical Connector,xe2x80x9d U.S. Pat. No. 5,588,843. That patent describes an electrical connector that includes two planar connector members positioned perpendicular to an axis of rotation and supported in rotational facing relation. One of the connector members has a set of concentric tracks, and the other has a corresponding set of protrusions positioned to contact the tracks. The two connector members are urged together by a spring so that the concentric tracts remain in electrical contact with the protrusions. A second patent to Sobhani, U.S. Pat. No. 5,690,498, entitled xe2x80x9cSpring Loaded Rotary Connector,xe2x80x9d teaches a similar connector in which the protrusions are replaced with dimples. Both of the foregoing Sobhani patents are incorporated herein by reference.
The Sobhani connectors work well in many applications. However, the complexity of making the protrusions or dimples increases the cost of making the connectors. Further, such connectors can be sensitive to shock, which can damage the protrusions or dimples. There is therefore a need for a more robust and less expensive means of providing rotational electrical contact.
The present invention is directed to a robust, inexpensive and rotatable electrical connector. In accordance with the invention, the connecter is used in conjunction with other parts to create a system of interconnected electrical components in which the individual components are easily removed for repair or to change the functionality of the system.
The inventive electrical connector includes a pair of wiring boards (e.g., printed-circuit boards) that each includes, on one side, two or more concentric conductors. The opposite sides of the two wiring boards include contacts that are electrically connected through the respective boards to the concentric conductors.
Each wiring board is held in place by a respective connector support. Contact is established between the two wiring boards when the supports are positioned so that the concentric conductors on the wiring boards face one another and are brought into electrical contact. This contact can be direct or through other components. For example, one embodiment includes a conductive elastomeric member between the wiring boards to allow some tolerance to ensure adequate conductive contact between opposing concentric conductors in the event that the wiring boards are not exactly parallel. In other embodiments, a spring or other elastic member urging one wiring board against the other supplies this tolerance.
The above-described wiring boards are used to advantage in a novel circuit module. The circuit module includes a printed circuit board, or other electrical component, sandwiched between a pair of wiring boards. The concentric conductors of the wiring boards face away from the electrical component so that the circuit module can be assembled in series with other modules much as batteries are assembled inside a flashlight. This simple configuration allows for easy assembly of systems that include circuit modules configured in accordance with the present invention, and further allows for easy substitution of modules within such systems.